Chainsaws are potentially dangerous tools even when operators exercise extreme caution during their use. Over the years, chainsaws have been manufactured to include braking mechanisms that are intended to function to stop the rotation of the saw chain about the saw bar in the event that the saw bar and the chain thereabout kick backwards toward the operator. These “kickback” brakes operate either through centrifugal forces or through impact of a front hand guard with the operator's support arm used to support and maneuver the chainsaw. In either case, the kickback brakes operate through the movement of various elements from active positions, where the saw chain is permitted to rotate about the chain guide, to brake positions, where the saw chain is braked. When the kickback brakes are activated, the saw chain is stopped through well-known typically spring biased mechanisms.
Chainsaws typically operate in such a manner that the saw chain may continue to rotate about the saw bar when the operator has let up on the throttle. This is known as “chain run down.” Even when the throttle is fully released, there is a chance that the saw chain may be moving at a rate fast enough to be dangerous. Attempts have therefore been made to associate components of the braking mechanism with the throttle to brake the saw chain upon release of the throttle and release the saw chain from the braked state upon squeezing the throttle. It is believed that these attempts have failed, because they provided a chainsaw having a throttle that was too difficult to squeeze and keep depressed, causing finger fatigue and shock to the finger squeezing the throttle trigger, when the front hand guard is activated. An example is provided in U.S. Pat. No. 4,683,660, wherein a link extends from components of the brake mechanism to the throttle such that squeezing the throttle pulls on the brake mechanism to release its braking of the saw chain, and letting up on the throttle allows the brake mechanism to return to a position that stops the moving saw chain. Similar chainsaw embodiments are provided in U.S. Pat. Nos. 4,594,780; 4,753,012; 5,813,123; and 6,842,987.
Although the prior art has addressed the inherent dangers in operating a chainsaw and has provided mechanisms in an attempt to make chainsaw operation safer, a need still exists for improved safety mechanisms that deal with chain run down. A further need exists for chainsaw mechanisms that reduce finger fatigue.